Gearbox/Synchros
 

So after owning an XJ (bulletproof great) and WG (great, until... dropped valve seat killed the engine) and WK (great) I wanted something with almost zero electronics so the TJ it is for my weekend car. The 4 litre straight 6 I had in my XJ suffered more abuse than any engine should and never missed a beat - thus the attraction of TJ instead of JK.

That boring preamble out of the way - I bought the 5 speed manual (2004) and it crunches downshifting from 3rd to 2nd unless changing at a really low speed. I can mitigate it by matching revs but it's strange to me.. normally syncros crap emselves 1st - 2nd. I've never in 25 years of driving had 'the grind' from 3rd to 2nd.

Is this a common thing for the 5 speed in the TJ's. As I said I've never encountered it before on any other car... is there a fix (and does it even matter, as I said matching revs mitigates it entirely).

It’s quite common and mostly a result of wear and tear due to age.

Type

https://wranglertjforum.com/threads/...r-grind.28397/

The US forums have heaps of threads about this.

Thanks. I hadn't even thought about looking towards US forums before trying an Aussie one.

Cheers.

hi
Change the oil, in the old days we often had to put different oil in manuals. Falcons and valiants... engine oil. Datsuns if customer complained we put Automatic trans oil in. Some Mercedes trucks Zf boxes had auto fluid in Manuals.
If some one put the wrong type of diff oil in the gearbox it will keep slipping on syncros instead of gripping. Or if they put the diff additive in the manual box it would be :hammer: .
At worst it could be syncros, there were trucks we had a fleet of 200 vehicles and we would modify the boxes so they selected further on the selector rail so they would stay in gear once they were a bit worn.
Go straight gear oil as without all the additives and start there. Easier to change the oil and you may get lucky. As PO. may have tried something better.:!:
good luck
Peter
jagonev12

Thanks mate... a simple thing to do and worth trying - I'd forgotten about the simple things to do so appreciate it - double clutching to smoothly go from 3rd to 2nd is no biggy but ultimately I'll have to deal with it.

Anyway when you mentioned Falcons and Valiants the R31 GTS Skyline was similar... manual box that after 80 odd thousand k's would grind but 1st to 2nd; different oil and 'wah la'. I suppose the R31 was only a bit later than the Datsun era so it makes sense heh.

The 5 speed gearbox has yellow metal sincro cones. You must not put oil with friction modifiers in it. The molly kills the sincro very quick. there has been plenty said about it on here over the years.

Yes - and Jagonev said exactly that: "Or if they put the diff additive in the manual box it would be :hammer: "